Automatic carburetor choke mechanism



NOV- 8, 1932- 3r w. MacMlLLAN 1,887,061

AUTOMATIC CARBURETOR CHOKE MECHANISM Filed Sept. 6, 1950 Patented Nov.8, 19u32`A p UNITED STATES PATENT OFFICE CHARLES wrom' mcmLLAN, oremanada, MASSACHUSETTS AU'roIlTA'rIc cAaBUnEron cnoxrz f Application measeptember s, 1930. septum. mazos.

This invention lis a carburetor choke mechanism which in conjunctionwith the throttle, the choke valve, and a thermostat-functionsautomatically to regulate the .carbure-- an automatic means of openinclosing, and

regulating the osition of t e carburetor o choke valveun er allconditions of engine temperature, and under all conditions of powerrequirements when the engine temperature is below its thermal normalcy.The advanta es of this invention lie'in the fact that it ren ers itunnecessary to manually operate the carburetor choke control, andthereby eliminates the necessity of regulating this control by hand whenstarting a cold engine. Furthermore, this invention eliminates thetendency to over-choke and under-choke the carburetor durin the runningperiod required by the engine to gain its normal temperature.

I declare the following to be an exact description of the invention. l

Referrin to the drawlng, Figure is fla skeleton, kinematic sketch of themechanism showing six different phase positions of the said mechanism.Figure 2 is a side elevation of an automobile engine showing thecarburetor and the mechanism applied to the.

choke valve. Figure 3 is a front elevation of the engine showing themechanism applied to the carburetor, and the thermostat control whichallows the choke 4valve to open as the engine temperature rises.l v-

A detailed description. of the invention is as follows. Referring toQthedrawing, numbers V1, 2, 3, .4, 5, and 6 denote different positions ofthe mechanism. 23 denotes the throttle control rod which, in anautomobile, connects the foot pedal with the carburetor throttle valve.'22 denotes anarm having a fixed pivot, 16, and'being connected to thethrottle rod, 23, by means ofthe pin joint, 14.

Number 17denotes an arm which is connectedy to arm 22 by means of a pinjoint denoted by 19, and to a slider denoted by 12 also by means of apin joint. 13 denotes an arm having a fixed pivot denoted by 21. Number11 denotes a slider to which the arm 13 is connected by l means of a pinjoint. 20 ,denotes a pin e'xtension of the carburetor choke valve. 10de-l notes an arm which is connected firmly to the pin 20, and whichoperates the choke valve thereby. 27 denotes a iixedstop post againstwhich the arm 10 may strike thus restricting the backward movement ofthis arm. 30 denotes' an arm which is operated from a thermostat, andwhich rotates thru a negative or positive angle as the temperature" ofthe engine increasesl or decreases respectively as viewed in Figure 1.Number 15 denotes the position assumed by the pin 'oint 14 when thethrottle is open, while 18 same conditions. 7 denotes an arc describedby a point on the arm 10 as this arm rotates;

the said point coinciding with the position of the center of the slider11 in phase position 10 pivot of the arm' 10 and' which holds this arm76 a ainst the thermostat-controlled arm 30.

umber 29.- denotes athermostat which in Figure 3 is shown to be incontact with the cylinder block where the actual engine Atemperaturegoverns its operation. 24 denotes .80

the carburetor. 25 denotes the throttle valve. Number 31 denotes theconventional butter- `ffiyvalve vof the throttle. Number 32 denotes thechoke valve.

A complete explanation of the operation of this invention'a-nd thekinematic movements 'of this 'mechanism' is as follows.

The correct: operation of a carburetorV choke valve under all condltlonsmust necessari ybe a' function of two variable factors, 90

requirement is controlled by means of the mechanism in this invention.The power required is obviously a lvarlable factor since an enginewillrun smoothly under a small 1C? j enotes the posi- 65 tion assumed by thepin joint 19 under the different, indi- 9a vidualxd'esigns. The 'variabe factor of power load when below its normal temperature even though thefuel mixture bathe-same as that required when the engine is running atits normal temperature. However, whilebthe engine is running in thiscondition if the load is suddenly increased, the richness or density .ofthe fuel mixture must simultaneously be increased to prevent thestopping of the engine. The present conventional means ofenriching thefuel mixture whenjrequired by a cold engine is by the manual operationofthe carburetor'choke control. This is 1nvariably necessary with allautomobile engines during the warming period required to bring theengine temperature up within its normal operating range. This inventionbrings together the change in engine temperature and the requiredchoking of the carburetor by means of a thermostat and the disclosedmechanism, both operatin in conjunction with each other to correct y andauto-A matically control the carburetor ,choke durin'g all of theforegoing conditions under which the engine must run. Referring must beclosed to a certain extentdepending e time of starting. This isautomatically per Vrmed i on the temperature. of the engine at by thethermostat-controlled arm 30 which is so adjusted in connection with thearm 10 that it will hold this arn'il in the lcorrect p0- sition forstarting the engine under all general temperature".y conditions. As theengine becomes warm the thermostat arm 30 rotates clockwise thusallowing the arm 10 to move likewise and thereby opening the chokevalve. At any time during the warming period required by the engine itmay be necessary to operate the choke valve. Such a moment will occurwhen the power. output is insufficient due to a fuel mixture which istoo thin to provide the combustion necessary for the power required atthe temperature under consideration. In order that the' choke valve mayoperate correctly; at any moment during the warming period it isnecessary to provide a means of steadily diminishing the allowableamount of choking action as the engine temperature rises. inventionmeets this" requirement by means of the arm 13 which rotates on thepivot 2l and the arm 10 which rotates about the pivot 20, the two armsbeing connected by means of to' Figure l of the drawing it will be notedthat The mechanism of this meager the slider 11. While rotating in aclockwise direction the slider 11 moves outwardly on the arm 10describing the arc denoted by 8, while a corresponding point on arm 10in position l describes the arc denoted by 7. At any time whenadditional power might be required the throttle would be suddenly openedcausing arm 22 to swing about its pivot 16 thus pulling the arm 13 andhence the arm 10 in a counterclockwise direction thereby choking thecarburetor. From Figure 1 it may be seen that the slider 11, during itsclockwise rotation, in being pulled counterclockwise by a succession ofmovements of the throttle arm 23, will move back each successive time toa consequence the arm 10 is moved countering less distant from the finalposition there- `by providing a diminishing amplitude of op-- eration ofthe choke valve.

The foregoing is evidentfrom the fact thatthe slider 11 must travel backover a greater segment on arc 8 than the corresponding segment on arc 7Thus when the mechanism isin posi-1 tion 3 the indicated movement of thethrottle: rod 23 moves the arm 10 counterclockwise to' position 2.Similarl from position 5 the arm 10 is moved bac responding to thenormal operating tempera'- turel the arms 17 and 13 lie in the samestraight line. Hence in this latter position a movement ofthe throttlearm has no further eifect on the mechanism.

tn operation themo'vements of this mechanism are 'precisely asheretofore described. The choke valve is closed or partly closed byan'o'penlng movement of thethrottle, and is `opened by means ofaspringas the thermostat arm which checks this' opening movementretreats due to" a..risingtempei'atui'e The mechanism is to be adjustedby setting the adjustable'pivots in the desired positions.- When theengine becomes warmed to its operating temperature no further choking.is necessary and, after this point is reached, any,

movement of the throttle has no further ef; feet on the choke valve, butwhen the enginey becomes cooled subsequent to-'stoppng it is evidentthat the thermostat arm moves so as ,tofpartl close the choke valve. Thether-" mostat t us effects both an opening and closirg movement of thechoke While the throttle e ects only a closing movement of the saidchoke. Furthermore, fsinooth o eration of rthe engine is inherentlyprovide for by the actual operation of the sliders on their re-l-spective arms. For example, as the throttle is suddenly opened at anymoment when the mechansm is in an intermediate position they frictioncaused by the sudden pressure of the sliders on their' respective armscauses the mechanism to move counterclockwise to the point less distantfromv the final outward position denoted by 6. In-

. to position 4. When the theIIIlOStat arm 30 reaches a position coriopiio

choke valve to which it is ap lied. Means of adjusting this mechanism oreach individual engine may be provided by means of changing the osit-ionof the fixed pivots 16 and 21, and-t e: stop post 27, with relation toeach other. This mechanism may be compactly inclosed in a box-likehousing for the purpose of improvin its appearance and protecting itagainst ust and possible damage.

vWhat I claim is: j

1. An automatic carburetor choke mechanism operating in conjunction witha throttle Valve control to which it is attached and a movablethermostat-controlled piece withv which it comes in contact,therebycorrectly correctly regulating the air-intake valve of acarburetor.

4. An automatic carburetor choke mechanism consistin of an arm beinattached to an extension Qa carburetor cho e valve, said extensionbeing. rotatable about its longitudinal axis in operating said valve,and said arm being perpendicular to said axis; a slider mounted on andbeing movable longitudinally along said'armyan arm being attached tosaidslider by means of a pin joint and also being attached to a fixedpivotand movable about said pivot; a second slider mounted on andbeinemovable along the last said arm; an arm ing attached to the lastsaid slider by means of a pin joint; a fourthl arm being movable aboutaxedpivot and being-connected to the last said arm by means of a pinjoint, said fourth arm being connected to a throttle control i rod bymeans of a pin joint.

5. An automatic carburetor choke mechanism consisting "of an arm beingattached to a carburetor .choke valve control; a second arm having andbeing movable about a fixed pivot and being connected to -first said armand movable longitudinally along first said arm at the point ofconnection; a third arm being connected to said second arm and linkingsaid second arm with a throttle valve control.

6. A11 automatic carburetor choke mechanism in which an arm extends fromthe choke valve control and operates said valve by 'means of a slider onsaid arm, said slider being attached by means of a gin joint to a secondarm, said second arm eing rotat- Lable about a xed pivot, said pivotbeing :eccentrically located with respect to the plvot of the first saidarm, an adjustable, fixed stop post against which the first said arm maystrike thereby restricting the backward movement of said arm and inconsequence restricting the chokingmovement of the choke valve.

7. An automatic carburetor choke mechanism consisting of two arms eachof which rota-tes about its own fixed pivot, said ivots beingeccentrically located, said arms ing connected and having relativemotion at the ointl of connection, one of the'y said arms ing the directmeans of operatin the carburetor choke valve and being held y means of aspring against a movable thermostat-controlled arm, saidthermostat-controlled arm being the means of restricting the movement inone direction of said choke valve operating arm.

/8. A. mechanism for automatically operating and regulating 'acarburetor choke valve by means of an arm being ivoted at one extremityon an extension o saidvalve; a slider bein confined to and movablelongitudinally a ongsaid arm a second arm bein pivoted at one extremityand attached to sai slider by means of a pin joint at its otherextremity; a second slider being confined to and movable longitudinallyalong said scond arm; a third arm being attached by means of a' in jointto .said second slider and being li ed with la throttle control lever, athrottle opening movement of said lever providing the force by means ofwhich the mechanism is actuated to correctly and automatically operatethe choke valve of a carburetor when an increased density of fuelmixture is required.

9. An automatic carburetorchoke mecha- .nism operating in conjunctionwith a throttle control arm and a thermostat-controlled arm to correctlyregulate the choke valve 'of a carsaid arms operating said choke vlvalve and having its movement in one direction rey stricted bysaid..-thermostat-controlled arm while'its movement in the oppositedirection is restricted by a xed stop, the other said arm beingconnected to a slider by'means of a pin joint and said slider beingattached to and movable along-the first said arm, a second slider beingattached to and movable along the second said arm, said secondA sliderhaving a pin joint to which a' third armV is attached, said third armbeing linked with said throttle control arm' thecomplete mechanism opatin as and for the purposev substantial?7 set orth.

In testimony whereo I ax my signature.

C. W. MAOMILDAN.

